Method of manufacturing a coil

Abstract: By applying a tension (a,b) to the conductor (21) to be cut off, and locally heating (22) the intended cutting position to provide a temperature difference of 20 to 300°C from other parts, the cutting position is lowered in tensile force as compared with other parts, and by applying a tension, the concentrated stress is added, and a large distortion is generated to cut off, so that the cutting position may be stabilized.

Description: FIELD OF THE INVENTION The present invention relates to a conductor cutting method suited to manufacture of coil parts to be used in electronic circuits of computer, television receiver, audio appliance and others, and also to coil parts. BACKGROUND OF THE INVENTION Recently, the multifunctional trend is notable in the fields of electric household appliances, office automation equipment and others, and electronic circuits are employed widely also outside the electric industries, such as production facility industry and automotive industry. Accordingly, the use of coil parts winding conductors is intensively increased. In manufacturing coil parts by winding conductors, hitherto, it is difficult to stabilize the cutting position of conductors, and the cutting method is one of the important subjects. A conventional cutting method of conductors of coil parts is explained below. Fig. 13 is an example of coil winding machine for winding a conductor around a winding body (hereinafter called bobbin). For the ease of understanding of the conventional conductor cutting method, its principle and operation are described while referring to Fig. 13. In Fig. 13, a mounting arm 1 has a bobbin 2 attached to its end as shown in the drawing. Opposite to the mounting arm 1, a spindle 9 is provided, and a conductor guide nozzle 7 is disposed at the front end of the spindle 9 through a flier 8, and a conductor 6 is supplied from this conductor guide nozzle 7. Fig. 13 shows the state of completely winding the conductor 6 around the bobbin 2. Explaining the operation of this winding machine, the mounting arm 1 mounted on a rotary shaft (not shown) is rotated and displaced in the direction of arrow A about the rotary shaft, and a next mounting arm accommodating an empty bobbin 2 moves to position 1a confronting the spindle 9, while the mounting arm 1 being opposite to the spindle 9 moves to position 1b. At this time, the conductor 6 wound on a terminal 4b of the bobbin 2 mounted on the mounting arm 1 moving to position 1b bridges between the terminal 4b of the bobbin 2 and the conductor guide nozzle 7. In this state, the flier 8 moves in the direction of arrow X, and the conductor guide nozzle 7 is positioned near a terminal 4a of the bobbin 2 mounted on the mounting arm 1 moving to the position 1a confronting the spindle 9. In actual operation, when the mounting arm 1 is rotated and displaced, the flier 8 moves simultaneously, and the conductor guide nozzle 7 is positioned near the terminal 4a, so that the conductor does not sag in this move. In this state, as the conductor guide nozzle 7 moves in the direction of arrow Y1 in a specific range about the terminal 4a, and moves in the direction of arrow X1, then moves in the direction of arrow Y2, and moves in the direction of arrow X2, then moves in the direction of arrow Z1, thus repeating, the flier 8 winds the conductor 6 near the root of the terminal 4a, thereby forming a winding wire 5a. At this time, a bridge conductor 6a between the terminal 4b of the bobbin 2 mounted on the mounting arm 1 moving to the position 1b and the terminal 4a of the bobbin 2 mounted on the mounting arm 1 moving to the position 1a confronting the spindle 9 is as shown in Fig. 13. After this action is complete, the flier 8 prepares for winding the conductor to the bobbin 2, and the spindle 9 and bobbin 2 coincide in the center, and the conductor guide nozzle 7 moves so as to be positioned inside of the flange of the bobbin 2. In this state, the flier 8 rotates about the bobbin 2 in the direction of  (or  '), and simultaneously moves reciprocally at a specific ratio in the direction of X' or X, thereby forming a coil 3. When this action is over, the previous action is repeated to form a winding wire 5b on the terminal 4b. The state of completion of this operation is shown in Fig. 13, and the same operation is repeated sequentially thereafter. Since the coil 3 wound in this way is wound by a continuous conductor, an extra bridge conductor 6a for bridging between the terminal 4a provided on the bobbin 2 winding this coil 3, and the terminal 4b of the bobbin 2 winding the previous coil 3, and it must be cut off and removed. The cutting and removing method of the conventional bridge conductor 6a is described below. Fig. 14 shows an example of cutting and removing the bridge conductor 6a in a partially magnified view of Fig. 13. In Fig. 14, the mounting arm 1 is moved to the position 1b in Fig. 13. A holding mechanism 10 comprises chuck claws 11a, 11b for holding the bridge conductor 6a, and moves in the direction of arrow B and in the direction of arrow B' in a specific range, and the chuck claw 11a is displaced in the direction of arrow C, while the chuck claw 11b is simultaneously displaced in the direction of arrow D, thereby holding the bridge conductor 6a. Firstly, the holding mechanism 10 moves in the direction of arrow B to the position where the chuck claws 11a, 11b hold the bridge conductor 6a. At this position, the chuck claw 11a is displaced in the direction of arrow C, and the chuck claw 11b is displaced in the direction of arrow D, thereby holding the bridge conductor 6a firmly. Fig. 14 shows the state of holding the bridge conductor 6a. In this state, the holding mechanism 10 moves in a specific range in the direction of arrow B'. At this time, the bridge conductor 6a is cut off as a tension is applied by the terminal 4b and chuck claws 11a, 11b. In such cutting method, however, stable cutting position is not obtained, and an extra conductor is left over at the terminal 4b, and the undesired conductor cannot be removed completely, and a short undesired conductor is left over. This short undesired conductor seriously affects the quality of the coil parts such as short circuit. SUMMARY OF THE INVENTION It is the object of the invention to present a conductor cutting method capable of securely stabilizing the cutting position when cutting a conductor of a coil and to stabilize the quality of coils. This object is achieved by the features of claim 1. Preferred embodiments of the invention are subject matter of the dependent claims. In this way, by applying a bending stress and a tension and cutting off with a temperature difference of 20 to 300°C with respect to other parts by heating the cutting position of the conductor, the change of tensile force by temperature difference can be utilized, and therefore the heated cutting position is lowered in tensile force as compared with the other parts, and by applying a tension, a concentrated stress is added to generate a large distortion, thereby cutting off. Generally, the conductor for composing a coil is formed within an insulating coat film of urethane resin, but by defining the upper limit of the temperature for locally heating the cutting position at 300°C or preferably 150°C the insulation performance of the insulating coat film of the coil portion is not lowered by heating. Or, by applying a bending stress and a tension and cutting off with a temperature difference of 20 to 300°C provided from other parts by heating the cutting position of the conductor, the heated cutting position is lowered in tensile force as compared with the other parts, and by applying a bending stress and a tension, a concentrated stress is added to generate a large distortion, thereby cutting off. Moreover, by the aforementioned conditions, the cutting position of the conductor is stable, and a short undesired conductor portion is not left over at the terminal, and any quality problem due to remaining of undesired conductor does not occur. From DE-B-2 061 949 a method and an apparatus for tip forming of wires, profiles and like work pieces by resistance heating is known, wherein the work piece is fixed between two spaced anchoring points and is heated in the portion between these anchoring points until the tensile strength of the work piece material decreases. The work piece is then stretched and during stretching is a thinned rupture location is formed by additionally heating the respective portion where the work piece should break. Thereby, a thinned tip of the work piece protruding from the remainder of the work piece material is formed. From Soviet Inventions Illustrated, Section P,Q; week D 31, September 9, 1981, Derwent Publications Limited, London and SU-A-778 954 a multi-layer material cutting method is known which involves preliminary drawing, followed by bending and cutting. According to this method, a multi-layer material, which can be a cable, is located horizontally in clamping jaws and drawn in two directions from the cutting plane. The material is then bent by the clamping jaws and cut by means of a rotating disc saw. Drawing reduces the stresses in the material, and the cutting force is reduced in proportion to the drawing force, so that the cutting force can be increased. Bending of the multi-layer material increases its transverse stiffness, draws the external layer and decreases resistance in penetration of the cutting tool. Any temperature application is not mentioned in this publication. In the following the invention is explained with reference to the accompanying drawings. BRIEF DESCRIPTION OF THE DRAWINGS Figure 1 (a)-(c) show cutting processes of a conductor. cutting method in a comparative example. Fig. 2 is a perspective view showing a comparative example of a conductor cutting method. Fig. 3 (a), (b) are perspective views of the conductor cutting method of Figure 2. Fig. 4 is a perspective view showing a comparative conductor cutting method. Fig. 5 (a), (b) are perspective views showing an example of result of cutting by the same conductor cutting method. Fig. 6 is a characteristic diagram showing the result of cutting the conductor by the same conductor cutting method. Fig. 7 is a plain view of a winding device by a conductor cutting method in an embodiment of the invention. Fig. 8 is a perspective view of the heating part of the same winding device. Fig. 9 (a) to (c) are plain views showing the action of the heating part of the same winding device. Fig. 10 is a perspective view of a coil part manufactured by the winding device by the conductor cutting method in the embodiment of the invention. Fig. 11 (a) is a perspective view of a coil part, and Fig. 11 (b) is a longitudinal sectional view of the same coil part. Fig. 12 is a perspective view of a coil part. Fig. 13 is a perspective view of a winding device in a conventional winding method. Fig. 14 is a perspective view showing a conductor cutting method of the same winding device. DESCRIPTION OF THE PREFERRED EMBODIMENTS Fig. 1 (a) to (c) show cutting processes of a comparative conductor cutting method. In Fig. 1, the cutting processes of a conductor 21 is described. Firstly, an infrared ray beam 24 emitted from an infrared ray beam source 23 is emitted to a cutting position 22 of the conductor 21. The cutting position 22 illuminated with the infrared ray beam 24 is heated to a higher temperature than the other parts by 20 to 300°C, preferably 20 to 150°C, so that the tensile force is lowered as compared with the other parts. In this state, as shown in Fig. 1 (a), both ends of the conductor 21 are pulled in the direction of arrows a and b, and a tension is applied. When the tension is continuously applied to the conductor 21, the cutting position 22 illuminated with the infrared ray beam 24 is deflected as shown in Fig. 1 (b). When the tension is further applied, the conductor 21 is cut off at the deflected portion as shown in Fig. 1 (c). In this way, by applying a tension and cutting off in the state of a temperature difference of 20 to 300°C, preferably 20 to 150°C, provided from other parts by heating the cutting position 22 of the conductor 21, the change of tensile force by temperature difference can be utilized, and therefore the heated cutting position 22 is lowered in tensile force as compared with the other parts, and by applying a tension, a concentrated stress is added to generate a large distortion, thereby cutting off. Fig. 2 shows a comparative example of cutting by heating the cutting position of a conductor, and applying a bending force and a tension. The cutting process of the conductor 21 is explained by referring to Fig. 2. First, as shown in Fig. 2, one end of the conductor 21 is held and fixed by a fixing chuck 27. Next, the cutting position 22 is fitted to a winding bar (round or square bar) 25 fixed by a block 26, and the conductor 21 is folded and a bending force is applied. The folded portion is heated by an infrared ray beam 24 emitted from an infrared ray beam source 23. The cutting position 22 illuminated with the infrared ray beam 24 is heated to a higher temperature from other parts by 20 to 300°C, preferably 20 to 150°C. In this state, a tension is applied in the direction of arrow a to the other end of the conductor 21 being not fixed. The cutting position 22 is heated by the infrared ray beam 24 and is lowered in tensile force, and the bending force and tension are applied, and the stress is concentrated in the bending force applied position by the synergistic effect, and therefore the cutting position 22 is cut off more stably than in the case of cutting by heating and applying tension as in the first example. In this way, when the cutting position 22 of the conductor 21 is folded and heated, and given a tension, the cutting position 22 becomes stabler. In the first and second examples, meanwhile, the cutting position 22 of the conductor 21 is heated by the infrared ray beam 24, but it is not limited to the infrared ray beam alone. In Fig. 3 (a), the cutting position 22 of the conductor 21 is heated by hot air 29 injected from a heating hot air nozzle 28, and in Fig. 3 (b), the cutting position 22 of the conductor 21 is heated by a laser beam 31 from a heating laser beam source 30. Thus, by heating the cutting position 22 of the conductor 21 by the hot air 29 or laser beam 31 and applying a tension, the conductor 21 can be cut off. In Fig. 3, the same parts as in Fig. 2 are identified with same reference numerals. In the foregoing examples, the cutting position 22 of the conductor 21 is heated from outside to a temperature higher than the other parts by 20 to 300°C, preferably 20 to 150°C, but the temperature difference may be also provided by self-heating by winding the conductor 21 around the winding bar 25 shown in Fig. 2. A third comparative example is described below with reference to Fig. 4. In the first and second examples, in order to cut off the conductor 21, the cutting position 22 of the conductor 21 is directly heated by a heat source. In Fig. 4, the conductor 21 is wound around the winding bar 25 to applying a bending force, and the winding bar 25 is heated by hot air 29 injected from a heating hot air nozzle 28, thereby heating the conductor 21 by conduction heat. The cutting process in Fig. 4 is explained below. First, the conductor 21 is wound around the winding bar 25 as shown in the drawing to form a winding part 32. In this case, the position first contacting with the winding start conductor 21 and winding bar 25 is the cutting position 22. One end of the wound conductor 21 is firmly held by a fixing chuck 27. The portion of the winding bar 25 not wound with the conductor 21 is heated by the hot air 29 blown out from the heating hot air nozzle 28. In this state, the other free end of the conductor 21 is pulled in the direction of arrow a to apply a tension to the conductor 21, so that it is securely cut off at the first contacting position of the conductor 21 and winding bar 25, that is, at the specified cutting position. An example of the result of the cutting experiment explained in Fig. 4 is shown in Fig. 5 (a), (b) and Fig. 6. Fig. 5 (a) is perspective view showing the state of cutting at the position of first contact between the conductor 21 and winding bar 25, in which the specified position is cut off. As shown in Fig. 5 (a), it is a conforming piece when cut at the specified position. Fig. 5 (b) shows cutting at other than specified position. As shown in Fig. 5 (b), it is a defective piece when cut at other than specified position. The result of the experiment is graphically shown in Fig. 6. In Fig. 6, the axis of ordinates represents the probability of the number of times of being cut at the position shown in Fig. 5 (a), out of the number of times of cutting the conductor 21 in the method explained in Fig. 4, that is, the conforming piece rate, and the axis of abscissas denotes the difference between the room temperature and the heating temperature of the winding bar 25 when cutting the conductor 21. In this experiment, if the temperature difference between the winding bar 25 and the room is 20°C or more, the conforming piece rate is 100%, and hence it is very easy to manufacture the device for heating the winding bar 25. In this way, the method of cutting the conductor 21 in the state of temperature difference provided from other parts by heating the cutting position 22 is effective means for stabilizing the cutting position 22, and is extremely effective for completely removing the undesired conductor of the conductor 21 wound on the coil terminal. An embodiment of the invention is described with reference to Figs. 7 to 9, wherein the undesired conductor of the conductor wound on the terminal of the coil part is cut. Fig. 7 is a plain view showing the constitution of the winding device of the coil part, in which mounting arms 33 are symmetrically mounted on four sides of a rotary shaft 34. The mounting arms 33 are provided with bobbins 35a, 35b, ..., and conductors possessing urethane resin insulating coat are wound and bridged continuously in the sequence of coil 36, bridge conductor 37 and coil 38. On the other hand, at the positioned side of the bobbin 35a, a hot air generator 39 is disposed in the configuration as shown in the drawing, and at the positioned side of the bobbin 35b, similarly, a hot air generator 40 is disposed in the configuration shown in the drawing. In the middle between the bobbin 35a and bobbin 35b, a holding mechanism 41 capable of tearing apart the bridge conductor 37 is disposed in the configuration shown in the drawing. This holding mechanism 41 is disposed to be movable in and out of the bridge conductor 37, and chuck claws 42a, 42b for pinching the bridge conductor 37 are provided at the front end, and the chuck claws 42a, 42b open and close about a pin 43, and are designed to hold the bridge conductor 37. This action is conducted by making use of air cylinder, solenoid valve, and electric circuit for controlling the solenoid valve, which are not shown in the drawing. The hot air generator 40 is described in detail while referring to Fig. 8. As shown in Fig. 8, a heating element 44 is to heat compressed air 45, and it is held by a holding pipe 46, and a current adjusted to a constant voltage through a conductor 47 is supplied to the heating element 44. By this current, the heating element 44 is heated to a specific temperature. A capillary coil 48 is tightly wound around the holding pipe 46, and this capillary coil 48 is hollow, and one end thereof is designed to feed the compressed air 45 supplied through a copper pipe 49 without escaping outside, and the other end is integral with a nozzle 50. The nozzle 50 is positioned so as to blow out the compressed air adjusted to a specific pressure linearly, and blow to the front end of the terminal part of a terminal 51 provided in the bobbin 35b. A holding plate 52 is for fixing the holding pipe 46 and copper pipe 49. The compressed air 45 supplied from outside into the copper pipe 49 is heated by the heating element 44 while passing through the capillary coil 48, and hot air 53 is blown out from the nozzle 50 to heat the terminal 51. The heated terminal 51 heats one end of the bridge conductor 37 by heat conduction. In this state, the chuck claws 42a, 42b move in the direction of arrow B up to the position for holding the bridge conductor 37, and the chuck claw 42a is further displaced in the direction of arrow C, and the chuck claw 42b is simultaneously displaced in the direction of arrow D, and the holding mechanism 41 firmly grasps the bridge conductor 37. Afterwards, the holding mechanism 41 moves a specific extent in the direction of arrow B', and applies a tension to the bridge conductor 37 to cut off. On the other hand, one end of the bridge conductor 37 entangled around the terminal 51a provided in the bobbin 35a is heated by the hot air generator 39 in the method described above, and is cut off by the holding mechanism 41. This action is described in detail while referring to Fig. 9 (a) to (c). Usually, as shown in Fig. 9 (a), the hot air generators 39, 40 are positioned at a specific distance from the bobbins 35a, 35b, and the holding mechanism 41 is positioned at a specific distance from the bridge conductor 37, so as not to disturb the coil winding action, terminal winding action, displacing action of the mounting arms 33, and other mechanism actions. Fig. 9 (a) shows the state in which winding process of coil and winding process on terminal are over, and the hot air 53 is blown to the terminal 51 by the hot air generators 39, 40. In this state, the holding mechanism 41 moves in the direction of arrow B, and holds the bridge conductor 37 by the chuck claws 42a, 42b. Fig. 9 (b) shows the state of holding the bridge conductor 37a. The holding mechanism 41, in the state of holding the bridge conductor 37 by the chuck claws 42a, 42b, moves in the direction of arrow B' as shown in Fig. 9 (c). The bridge conductor 37 is held by the chuck claws 42a, 42b, and as the holding mechanism 41 moves in the direction of arrow B', a tension is applied between the terminal 51a and terminal 51, and chuck claws 42a, 42b, and it is cut off at the terminal 51a and terminal 51. The cut-off bridge conductor 37 is discharged by a mechanism not shown in the drawing as the chuck claws 42a, 42b are cleared, thereby finishing the cutting process. Thus, the winding device in the embodiment comprises hot air generators for heating the terminals winding the conductor, when cutting the conductor, and a holding mechanism capable of tearing apart the conductor to be cut off, and the conductor can be cut off from the terminal by displacing the holding mechanism holding the conductor to be cut off by always heating the terminal when cutting. As a result, as shown in Fig. 10, lead wires 52 at both ends of the coil 38 wound around the bobbin 35 are wound on the terminal 51, and the ends of the lead wires 52 are not left over projecting from the terminal 51, so that a coil part with stable quality is obtained. A coil part wherein a conductor is cut off by the foregoing conductor cutting method is described below. Fig. 11 relates to a coaxial rotary transformer for exchanging signals between the rotary head and fixed side to be used in a video tape recorder or the like. In Fig. 11, an inner coil 61 is concentrically assembled in an outer coil 62. The inner coil 61 comprises plural circumferential grooves 64 for signal coil on the outer circumference of a cylindrical core 63, circumferential grooves 65 for short ring between these circumferential grooves 64 for signal coil, and a plurality of longitudinal grooves in the height direction, and a signal coil 66 is wound around circumferential grooves 64 for signal coil, and a short ring coil 67 winding the conductor two turns or more each is disposed in the circumferential grooves 65 for short ring, and the lead wire of the signal coil 66 is drawn out through the longitudinal groove, and is connected to a terminal 69 of a terminal plate 68 coupled with the lower end of the cylindrical core 63, and the short ring 67 is wound about each circumferential groove 65 for short ring, and the winding start and winding end of the short ring coil 67 are connected as being wound on one terminal 69 of the terminal plate 68. The outer coil 62 comprises plural circumferential grooves for signal coil 71 and several longitudinal grooves in the inner circumference of a cylindrical core 70, and a signal coil 72 is wound in the circumferential grooves 71 for signal coil, and the lead wire of the signal coil 72 is passed through the longitudinal grooves, and is connected with a terminal 74 of a terminal plate 73 coupled with the upper end of the cylindrical core 70. The signal coils 66 and 72 of the inner coil 61 and outer coil 62 are combined to confront each other. In the coaxial type rotary transformer in such constitution, same as in the embodiment, the lead wire of the signal coil 66 is wound around the terminal 69, and the lead wire of the signal coil 72 is wound around the terminal 74, and by applying a tension while heating the terminals 69, 74, short undesired conductor is not left over at the terminals 69, 74, so that quality problems due to remaining of undesired conductor may be eliminated. Fig. 12 (a), (b) is a flyback transformer used in television receiver or the like. Fig. 12 (a) is a sectional view of an entire flyback transformer, and Fig. 12 (b) is a sectional view of a high voltage coil part. A low voltage bobbin 75 turns around a low voltage coil 76, and a high voltage bobbin 78 winding a high voltage coil 77 in division is mounted on this low voltage bobbin 75. In the upper part and lower part of the high voltage bobbin 78, rectifying diodes 79 connected to the winding start side of the high voltage coil 77 are disposed. In the upper part of the high voltage bobbin 78, one end of an anode lead wire 80 is press-fitted. A magnetic core 81 is assembled into the assembly of such low voltage bobbin 75 and high voltage bobbin 78, and an insulation case 82 put over the entire surface to compose the flyback transformer. The lead wire of the low voltage coil 76 turning around the low voltage bobbin 75 is wound on a terminal 83. The lead wire of the high voltage coil 77 turning around the high voltage bobbin 78 is wound on a terminal 84. In thus composed flyback transformer, same as in the embodiment, the lead wire of the low voltage coil 76 is wound the terminal 83, and the lead wire of the high voltage coil 77 is wound around the terminal 84, and by applying a tension while heating the terminals 83, 84, short undesired conductor is not left over at the terminals 83, 84, so that the quality problem due to remaining of undesired conductor may be eliminated.

Claims: A method of manufacturing a coil comprised of a conductor (21) wound on a bobbin (2) in which a short, undesired portion (6a) of the conductor is not left over at a terminal (4b) of said coil (3), wherein said conductor (21) is cut by simply applying a bending stress and a tension to the conductor (21) outside said bobbin (2) while a cutting position (22) of the conductor (21) at said terminal (4b) is in the state of a temperature difference of 20 to 300°C with respect to other parts of the conductor by heating the cutting position (22) of the conductor (21). The method of claim 1 wherein the temperature difference is 150°C maximum. The method of claim 1 or 2 wherein the cutting position (22) of the conductor (21) is heated by infra red irradiation (24). The method of claim 1 or 2 wherein the cutting position (22) of the conductor (21) is heated by a laser beam (31). The method of claim 1 or 2 wherein the cutting position (22) of the conductor (21) is heated by hot air (29).

Inventors: HIROSE TOSIAKI, KORESAWA SABURO, NISHIDA KAZUNORI, HIROSE, TOSIAKI, KORESAWA, SABURO, NISHIDA, KAZUNORI
Applicants: MATSUSHITA ELECTRIC IND CO LTD, MATSUSHITA ELECTRIC INDUSTRIAL CO., LTD.
Application year: 1994
Main classification: H01F41
IPC codes: B21F11, B26F3, H01B13, B21C5, H01F41